Electroactive high storage capacity polyacetylene-co-polysulfur materials and electrolytic cells containing same

ABSTRACT

The present invention relates to novel electroactive energy storing polyacetylene-copolysulfur (PAS) materials of general formula (C 2  S x ) n  wherein x is greater than 1 to about 100, and n is equal to or greater than 2. This invention also relates to novel rechargeable electrochemical cells containing positive electrode materials comprised of said polyacetylene-co-polysulfur materials with improved storage capacity and cycle life at ambient and sub-ambient temperatures.

BACKGROUND OF THE INVENTION

This invention relates to novel electroactive energy storingpolyacetylene-co-polysulfur (PAS) materials of general formula (C₂S_(x))_(n) wherein x is greater than 1 to about 100, and n is equal toor greater than 2. This invention also relates to novel rechargeableelectrochemical cells containing positive electrode materials comprisedof said polyacetylene-co-polysulfur materials with improved storagecapacity at ambient and sub-ambient temperatures.

Batteries are used in almost all portable consumer electronic productsfrom flash lights to lap top computers. Over the years, considerableinterest has been shown in developing lighter weight high energy-densityrechargeable batteries for many applications including electricvehicles. In this regard, thin film solid state batteries using thepolyacetylene-co-polysulfur cathode materials of this invention areparticularly well suited for use in many consumer applications becauseof their high energy to weight ratio.

Two main types of cathode materials used in the manufacture of thin filmlithium and sodium batteries are known in the art. The first materialsinclude transition metal chalcogenides, such as titanium disulfide withalkali metals as the anode. For example, among the cathode activechalcogenides, U.S. Pat. No. 4,049,879 lists transition metalphosphorous chalcogenides. Other U.S. patents, such as U.S. Pat. Nos.4,143,214, 4,152,491 and 4,664,991 describe cells wherein the cathode isa carbon/sulfur based material, generally of the C_(x) S formula where xis typically 10 or larger.

U.S. Pat. No. 4,143,294 to Chang, et al. describes cells having cathodescontaining C_(x) S wherein x is a numerical value from about 4 to about50. U.S. Pat. No. 4,152,491 to Chang et at. relates to electric currentproducing cells where the cathode-active materials include one or morepolymer compounds having a plurality of carbon monosulfide units. Thecarbon monosulfide unit is generally described as (CS)_(x), wherein x isan integer of at least 5, and may be at least 50, and is preferably atleast 100. In both cells developed by Chang, et al. the energy storagecapacity is limited because there is a low density of sulfur-sulfurbonds.

U.S. Pat. No. 4,664,991 to Perichaud, et al. describes a substancecontaining a one-dimensional electric conducting polymer and at leastone polysulfurated chain forming a charge-transfer complex with thepolymer. Perichaud, et al. use a material which has two components. Oneis the conducting polymer, which is selected from a group consisting ofpolyacetylenes, polyparapheniylenes, polythiophenes, polypyrroles,polyanilines and their substituted derivatives. The other is apolysulfurated chain which is in a charge transfer relation to theconducting polymer. The polysulfurated chain is formed by hightemperature heating of sulfur with the conjugated polymer. As a resultof using this material, the cell of Perichaud, et at. exhibits a fairlylow voltage of only 2.0 V against lithium.

In a related approach, a PCT application (PCT/FR84/00202) of Armand etal. describes derivatives of polyacetylene-co-polysulfurs comprisingunits of R_(x) (CS_(m))_(n) wherein R is hydrogen, alkali metal, ortransition metal, x has values ranging from 0 to values equal to thevalence of the metal ion used, values for m range from greater than 0 toless than or equal to 1, and n is unspecified. ;Structures proposed forthese materials are of the type: ##STR1## wherein such materials arederived from the reduction of polytetrafluoroethylene orpolytrifluorochloroethylene with alkali metals in the presence ofsulfur, or by the sulfuration of polyacetylene with vapors of sulfurmonochloride at 220° C. Although these materials are electrochemicallyactive, they suffer from low storage capacity owing to low SIC ratiosand a limited number of S-S bonds in the materials. These materials canhave a considerable amount of residual hydrogen, fluorine, and chlorineatoms in their backbones depending on the method of synthesis.

U.S. Pat. Nos. 4,833,048 and 4,917,974 to De Jonghe, et al. describe aclass of cathode materials made of organo-sulfur compounds of theformula (R(S)_(y))_(n) where y=1 to 6; n=2 to 20, and R is one or moredifferent aliphatic or aromatic organic moieties having one to twentycarbon atoms. One or more oxygen, sulfur, nitrogen or fluorine atomsassociated with the chain can also be included when R is an aliphaticchain. The aliphatic chain may be linear or branched, saturated orunsaturated. The aliphatic chain or the aromatic rings may havesubstituent groups. The preferred forfit of the cathode material is asimple dimer or (RS)₂. When the organic moiety R is a straight or abranched aliphatic chain, such moieties as alkyl, alkenyl, alkynyl,alkoxyalkyl, alkythioalkyl, or aminoalkyl groups and their fluorinederivatives may be included. When the organic moiety comprises anaromatic group, the group may comprise an aryl, arylalkyl or alkylarylgroup, including fluorine substituted derivatives, and the ring may alsocontain one or more nitrogen, sulfur, or oxygen heteroatoms as well.

In the cell developed by De Jonghe, et al. the main cathode reactionduring discharge of the battery is the breaking and reforming ofdisulfide bonds. The breaking of a disulfide bond is associated with theformation of an RS₋ M⁺ ionic complex. The organo-sulfur materialsinvestigated by De Jonghe, et al. undergo polymerization (dimerization)and de-polymerization (disulfide cleavage) upon the formation andbreaking of the disulfide bonds. The depolymerization which occursduring the discharging of the cell results in lower weight monomericspecies which can dissolve into the electrolyte, thereby severelyreducing the utility of the organo-sulfur material as cathode-activematerial. The result is an unsatisfactory cycle life having a maximum ofabout 200 deep discharge-charge cycles, more typically less than 100cycles as described in J. Electrochem Soc., Vol. 138, pp. 1891-1895(1991). In particular, the organo-sulfur materials developed by DeJonghe, et al., are highly unstable in the presence of high conductivityliquid, plasticized polymer, or gel electrolytes.

A significant additional drawback with the organo-sulfur materialsdeveloped by De Jonghe, et al. is the slow kinetics of oxidation andreduction at ambient temperatures, severely reducing the power output ofcells incorporating cathodes made with these organo-sulfur materials.The slow kinetics result from the oxidation and reduction being relatedto the formation and breaking, respectively, of disulfide bonds onnon-conjugated, non-conductive materials.

Despite the various approaches proposed for organo-sulfur cathodematerials, there remains a need for inexpensive cathode materials havinghigh storage capacity, high discharge rates and very long cycle lives atambient and sub-ambient temperatures.

It is, therefore, a primary object of this invention to provide newpolyacetylene-copolysulfur based cathode materials for thin film solidstate batteries which are inexpensive, yet avoid the limitationsexisting in the prior art, while offering performance characteristicsmuch higher than those of known materials.

It is another object of this invention to provide new cathode materialshaving as the active material polyacetylene-co-polysulfur (PAS) polymerswhich do not undergo polymerization and de-polymerization upon oxidationand reduction.

It is yet another object of this invention to provide a method of makinga solid state rechargeable battery including the novel cathode of theinvention.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novelelectroactive energy storing polyacetylene-co-polysulfur (PAS) materialuseful as a solid state cathode material in rechargeable batteries. Inits fully charged or oxidized state, the PAS material can be representedby the formula I, ##STR2## wherein x ranges from greater than 1 to about100, n is equal to or greater than 2, and said PAS material does notcontain aliphatic or aromatic moieties. Said PAS material is furthercharacterized by the incorporation of large fractions of polysulfurcomponents, which on electrochemical reduction in an electrolytic cell,provides the exceptionally high storage capacity per unit weight ofmaterial. In contrast to materials presently known in the art, the PASmaterials of the present invention undergo oxidation and reduction withthe formation and breaking, respectively, of multiple sulfur-sulfurbonds which are attached to conjugated polymer backbone structures thatprovide good electron transport and fast electrochemical kinetics atambient temperatures and below. Said PAS materials when used as cathodematerials in battery cells, may be optionally mixed with conductivecomponents and binders to further improve electrochemical recycleabilityand capacity of said cathode active material.

One embodiment of the present invention relates to PAS compositions offormula I prepared by the reaction of acetylene with a metal amide, suchas sodium amide or sodium diisopropylamide, and elemental sulfur in asuitable solvent, such as liquid ammonia. Although the detailedstructure of such PAS materials has not been completely determined,available structural information suggests that these compositions arecomprised of one or more of the structural units of formulas II-VII;##STR3## wherein m is the same or different at each occurrence and isgreater than 2; and the relative amounts of a, b, c, d, e, and f in saidPAS materials can vary widely and will depend on the method ofsynthesis. Preferred compositions are those wherein m is greater than 3,and especially preferred compositions are those wherein m is on theaverage equal to or greater than 6. A key feature of these compositionsis that electrochemical reduction and oxidation need not lead todepolymerization and repolymerization of the polymeric backbone.Further, the polymer backbone structure contains conjugated segmentswhich may facilitate electron transport during electrochemical oxidationand reduction of the polysulfur side groups, wherein electrochemicalreduction and oxidation of the conjugated backbone segments does notoccur. PAS materials of the present invention typically have elementalcompositions containing between about 50 wt. % and 98 wt. % sulfur.Preferred PAS compositions are those that have elemental compositionscontaining between about 80 wt. % and 98 wt. % sulfur.

It is another object of this invention to provide a rechargeable, solidstate electric current producing cell capable of operating at ambienttemperatures and below, which is comprised of:

(a) an anode which is comprised of one or more alkali or alkaline earthmetals;

(b) a novel cathode having as the cathode active material one or morepolyacetylene-copolysulfur compounds which can be formulated as (C₂S_(x))_(n) wherein x is from greater than 1 to about 100, and n isgreater than or equal to 2; and

(c) an electrolyte which is chemically inert with respect to the anodeand the cathode and which permits the transportation of ions between theanode and the cathode.

The anode material may be an elemental alkali metal or an alkali-metalalloy including the mixture of an elemental alkali metal and one or morealloys made from an element selected from the Periodic Table Group IAand IIA metals. Lithium and sodium are useful materials for the anode ofthe battery of the invention. The anode may also be alkali-metalintercalated carbon such as LiC_(x) where x is equal to 6 or greater.Also useful as anode materials of the present invention are alkali-metalintercalated conjugated polymers, such as lithium, sodium or potassiumdoped polyacetylene, polyphenylene, and the like.

The cathode employed in the battery of the invention as the cathodeactive material is comprised of a PAS material of the formula (C₂S_(x))_(n), wherein x is from greater than 1 to about 100, and n is anumerical value greater than or equal to 2, and preferably greater than10.

The electrolytes used in the battery cells of the present inventionfunction as separator materials between the anodes and cathodes as wellas a medium for storage and transport of ions. In principle, any liquid,solid, or solid-like material capable of storing and transporting ionsmay be used. Particularly preferred are solid electrolyte separatorscomprised of polyethers, polyimides, polyphosphazenes,polyacrylonitriles (PAN), polysiloxanes, polyether graftedpolysiloxanes, blends of the foregoing, derivatives of the foregoing,copolymers of the foregoing, crosslinked and network structures of theforegoing, and the like to which is added an appropriate electrolytesalt.

A variety of solid gel-type electrolytes are also useful in the practiceof this invention. Illustrative of useful gel-type electrolytes arepolyacrylonitriles, sulfonated polyimides, cured divinyl polyethyleneglycols, cured polyethylene glycol-bis-(methyl acrylates), and curedpolyethylene glycol-bis-(methyl methacrylate) which have been swollenwith propylene carbonate (PC), ethylene carbonate (EC), glymes, lowmolecular weight polysiloxanes, and mixtures thereof.

Especially useful solid and gel-type electrolytes are those comprisingdivinyl polyethylene glycols, polyethylene glycol-bis-(methylacrylates), or polyethylene glycol-bis-(methyl methacrylate) which hasbeen cured (crosslinked) using UV, x-ray, gamma ray, electron beam, orother ionizing radiation.

It is another object of this invention to provide a method of making thesolid state batteries incorporating the novel cathode materials of thepresent invention. The method of making the cells of the presentinvention is particularly preferred for use in applications requitinghigh energy storage capacity.

It is still another object of this invention to provide solid statebatteries having higher specific energy and higher current than has beenpreviously achieved with organo-sulfur cathode materials.

It is a further object of this invention to provide batteries havinglong shelf life and a low rate of self-discharge.

These and other objects of this invention will be apparent from thefollowing description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cyclic voltammogram of PAS (made from the polymerizationof acetylene in the presence of a metal amide and sulfur) in anelectrolyte consisting of dimethylsulfoxide with 0.1 molar concentrationof tetraethylammonium perchlorate at a sweep rate of 50 mV/sec at roomtemperature.

FIG. 2 shows the cyclic voltammogram of ((C₂ H₅)₂ NCSS)₂ in anelectrolyte consisting of dimethylsulfoxide with 0. 1 molarconcentration of tetraethylammonium perchlorate at a sweep rate of 50mV/sec at room temperature.

DETAILED DESCRIPTION OF THE INVENTION

The cyclic voltammograms shown in FIGS. 1-2 illustrate the fundamentaldifference between PAS materials of the present invention andorgano-sulfur materials disclosed in the art whose electrochemicalactivity is based on breaking and reforming of disulfide bonds. In thecase of PAS materials the oxidation and reduction peaks are closelyaligned on the voltage axis indicative of fast, reversibleelectrochemical kinetics. In the case of ((C₂ H₅)₂ NCSS)₂, which isrepresentative of the materials disclosed by De Jonge et al. containingdisulfide bonds, and which polymerizes (dimerizes) and de-polymerizes(cleaves) by the forming and breaking of said disulfide bonds,respectively, during electrochemical oxidation and reduction, there is aspread of about 2 volts between the oxidation and the reduction peaks.This is indicative of very slow electrochemical kinetics associated withbond breaking and formation.

It is clear from these experimental results that PAS behaves like aconjugated polymeric material which is fundamentally different in itsstructure and electrochemical function compared with the mate,rialsdeveloped by De Jonghe et al. and Armand et at. This fundamentaldifference structurally and electronically is the cause for thesubstantially higher capacity and much improved electrochemical kineticsat room temperature.

Novel rechargeable battery cells of the present invention comprise threeessential components. One essential component is an anode material. Theanode may comprise any metal capable of functioning as a negativeelectrode in combination with the cathode materials of the presentinvention. Illustrative of useful anode materials of this invention areone or more metals selected from the group consisting of metalsbelonging to Group IA and Group IIA in the Periodic Table of theelements, such as lithium, sodium, potassium, magnesium, calcium, andthe like. Also useful in the practice of this invention are anodescomprised of alloys, mixtures, composites, intercalated carbons,intercalated conjugated polymers, and the like, of the aforementionedalkali and alkaline earth metals. Illustrative of such compositions aresodium-lithium alloys, lead-sodium alloys, lithium-fin alloys,lithium-silicon alloys, lithium intercalated carbons, lithium dopedpolyacetylene, sodium doped polyphenylene, and lithium intercalatedgraphite. Preferred anodes in the practice of this invention are thosecomprised of alkali metals. More preferred are those comprised oflithium and/or sodium. Most preferred are anodes comprised of lithiumfoils of thickness from about 2 microns to about 250 microns.

Another essential component in the novel battery cells of the presentinvention is a cathode material comprised of apolyacetylene-co-polysulfur material of general formula I; ##STR4##wherein x can range from greater than 1 to about 100, and n is equal toor greater than 2. Preferred anode materials are those wherein x isgreater than 2, and n is equal to or greater than 5. Particularlypreferred cathode materials are those wherein x is equal to or greaterthan 6, and n is greater than 5.

Also illustrative of useful cathode materials of the present inventionare composite cathodes comprised of:

(a) PAS materials of formula I,

(b) a non-aqueous electrolyte, and

(c) a conductive filler.

Useful non-aqueous electrolytes in said composite cathodes can be thesame or different from those used in the construction of completebattery cells. A complete description of useful electrolytes in thecomposite cathodes of the present invention is presented below.

Useful conductive fillers are any conductive materials that can enhancethe electrical connectivity between the current collectors and theelectroactive cathode components in the cell. It is desirable that saidconductive fillers be inert to the components of the cell under theintended operating conditions of the cell. Particularly preferredconductive fillers are conductive carbons; conductive acetylene blacks;graphites; metal powders, flakes and fibers; and electrically conductivepolymers such as polyanilines, polyacetylenes, polypyrroles,polythiophenes, polyphenylenes, polyphenylene-vinylenes,polythienylene-vinylenes, and derivatives thereof. Additionally,composite cathodes useful in this invention may contain other polymericor non-polymeric binder materials that facilitate the formation,fabrication, and assembly of battery cells in desired configurations.Such optional materials are known to those skilled in the art of cathodefabrication an include materials such as polytetrafiuoroethylene andother fluorinated polymers, SBR rubbers, EPDM rubbers, and the like.

The third essential component of the battery cells of the presentinvention is an electrolyte. Illustrative of useful electrolytes in thepractice of this invention are electrolytes that are chemically andelectrochemically inert with respect to the anode and cathode materialsand which permit the migration of ions between the anode and cathode atdesired use temperatures. Preferred electrolytes are those that allowfor transport of ions at ambient temperatures and below. Particularlypreferred are those capable of operating between about -40° C. and +120°C.

Electrolyte systems which have application to both lithium and sodiumbased rechargeable batteries can be employed in the fabrication of thecell of the invention, such as solid polymer electrolytes; single-ionconducting polymer electrolytes, high conductivity gel polymerelectrolytes, and liquid organic electrolytes. Particularly usefulelectrolytes for use in cells of the present invention are single ionconducting polymer electrolytes with highly delocalized anionic moietiescovalently attached to the polymer backbone to achieve high specificlithium ion conductivity, as described in U.S. Pat. No. 4,882,243. Theadvantages of polymer electrolytes with exclusive cation conduction arereduced cell polarization deriving from low anion mobility, reducedvolume changes in the cathode from intercalation of ion clusters, andreduced salt-induced corrosion on the current collectors. Roomtemperature conductivities for single ion conducting polymerelectrolytes described in U.S. Pat. No. 4,882,243 are in the range of10⁻ to 10⁻⁵ S/cm.

A variety of gel-polymer electrolytes have been discovered to be usefulin the practice of this invention. These electrolytes consist of a highmolecular weight polymer matrix into which is dissolved an electrolytesalt, then subsequently swollen with a low molecular weight liquid whicheffectively acts as a plasticizer for the salt-polymer matrix. These lowmolecular weight liquids are referred to as gelation agents and aregenerally common organic solvents or liquid oligomers. Any organicliquid capable of swelling said salt-polymer matrix can be used as agelation agent so long as it is stable to the selected cathode and anodein the battery cell. A substantial increase in electrolyte conductivitycan be achieved by introducing these gelation agents into saidsalt-polymer blends.

Illustrative of useful polymer matrices for gel polymer electrolytes inhigh energy density batteries of the present invention are those derivedfrom polyethylene oxides, polypropyleric oxides, polyacrylonitriles,polysiloxanes, polyimides, polyethers, sulfonated polyimides, Nafion™resins, divinyl polyethylene glycols, polyethylene glycol-bis-(methylacrylates), polyethylene; glycol-bis(methyl methacrylate), blends of theforegoing, derivatives of the foregoing, copolymers of the foregoing,crosslinked and network structures of the foregoing, and the like.Useful ionic electrolyte salts for gel-polymer electrolytes includeMClO₄, MAsF₆, MSO₃ CF₃, MSO₃ CH₃, MBF₄, MB(Ph)₄, MPF₆, MC(SO₂ CF₃)₃,MN(SO₂ CF₃)₂, ##STR5## like, where M is Li or Na. Other electrolytesuseful in the practice of this invention are disclosed in U.S. patentapplication Ser. No. 192,008.

Useful gelation agents for gel-polymer electrolytes include ethylenecarbonate (EC), propylene carbonate (PC), N-methyl acetamide,acetonitrile, sulfolane, 1,2-dimethoxyethane, polyethylene: glycols,1,3-dioxolanes, glymes, siloxanes, and ethylene oxide grafted siloxanes.Particularly preferred gelation agents are those derived from graftcopolymers of ethylene oxide and oligomers of poly(dimethyl siloxane) ofgeneral formula VIlI, ##STR6## wherein u is an integer equal to orgreater than 1,

v is an integer equal to or greater than 0 and less than about 30, and

the ratio z/w is equal to or greater than 0.

Values for u, v, w, and z can vary widely and depend on the desiredproperties for said liquid gelation agent. Preferred gelation agents ofthis type are those wherein u ranges from about 1 to 5, v ranges fromabout 1 to 20, and the ratio z/w is equal to or greater than 0.5. Anespecially preferred composition of formula VIII is that in which u isequal to 3, v is equal to 7, and the ratio of z to w is 1.

These liquid gelation agents themselves are useful solvents to formliquid electrolytes which provide other effective electrolyte systemsfor the cells of the invention. For example, glymes with lithium salts,such as LiAsF₆, are useful liquid electrolytes. Likewise, compositionsof formula VIII together with Li(SO₂ CF₃) are especially useful asliquid electrolytes.

Battery cells comprising PAS cathodes can be made in a variety of sizesand configurations which are known to those skilled in the art.Illustrative of useful battery design configurations are planar,prismatic, jelly-roll, W-fold, and the like. These configurations arenot to be construed as limitations on the scope of this invention asother designs are anticipated.

In batteries of the present invention, the main design concerns are thekinetics and chemical and electrochemical reversibility of thereduction/oxidation reactions, the density of available sulfur atoms,and the miscibility of oxidation and reduction products with the polymerelectrolyte. During the discharge of the cells of this invention, thePAS polymer is reduced accompanied by the insertion of Li⁺ ions into thecathode from the electrolyte to maintain charge neutrality. In contrastto the materials disclosed in U.S. Pat. Nos. 4,833,048 and 4,917,974,the polyacetylene-copolysulfur materials of the present inventionundergo oxidation and reduction with the formation and breaking ofmultiple sulfur-sulfur bonds attached to conjugated structures whichprovide good electron transport and fast electrochemical kinetics atambient temperatures and below. An advantage of using PAS as the cathodeactive material is the high density of sulfur atoms which results in ahigh charge storage density during oxidation-reduction. This isaccompanied by a high density of Li⁺ ions inserted for chargeneutrality, resulting in a high capacity.

In contrast to the organo-sulfur materials developed by De Jonghe, etal. PAS need not undergo polymerization/de-polymerization upon chargeand discharge, thereby maintaining the integrity of the polymer backboneand improving cathode utilization during repeated charge and discharge.

Table 1 summarizes the superior performance of battery cells comprisedof PAS anodes of formula I relative to state-of-the-art rechargeablebattery systems presently commercialized or under development. The PASbased cells exhibit a volumetric energy density advantage of from 2 to 3times, and a gravimetric energy density advantage of from 1.7 to 3.5times better than presently known rechargeable cells in a AAconfiguration.

                  TABLE 1                                                         ______________________________________                                        Performance comparisons of PAS based rechargeable                             cells relative to other advanced                                              rechargeable systems in AA cell configurations                                Electrochemical                                                                            Volumetric Energy                                                                           Gravimetric Energy                                 System       Density (Whr/L)                                                                             Density (Whr/Kg)                                   ______________________________________                                        Li/PAS cells of                                                                            430-500       175-260                                            formula I                                                                     Lithium Ion  215           100                                                Nickel Metal Hydride                                                                       180-200       60-75                                              Nickel Cadmium                                                                             120-140       40-50                                              (premium)                                                                     ______________________________________                                    

The following specific examples are presented to more particularlyillustrate the invention, and should not be construed as limitations onthe scope and spirit of the invention.

EXAMPLES Example 1 Preparation of Polyacetylene-co-Polysulfur FromAcetylene and Sulfur

Into 250 mL of liquid ammonia with stirring was added 27.3 g (0.7 mol)of sodium amide. Through this solution was passed acetylene gas for 2.5hours. To this reaction mixture was then added portion-wise 67.2 g (2.1tool) of sulfur. The reaction mixture was stirred for an additional 7.5hours, then 37.45 g (0.7 mol) of ammonium chloride was slowly added. Thereaction mixture was allowed to warm to room temperature overnight, then350 mL of water was added to the residue. The solid product wasfiltered, washed with water, then washed with acetone, and dried undervacuum. The yield was 59.5 g; elemental analysis indicated 85 wt. %sulfur.

Preparation of Polyacetylene-co-Polysulfur Composite Cathodes Example 2

A mixture of 50% by weight PAS prepared by the general procedure ofExample 1, 20% polyethylene oxide-LiSO₃ CF₃ and 30% acetylene black wassuspended in acetonitrile/isopropanol (1:2) to form a slurry. The slurrywas ground into fine particles and was then cast as a film 25-100 μmthick on a 25 μm thick nickel foil. The entire unit was dried in avacuum oven at 40° C.-80° C. for 24 hours.

Example 3

A mixture of 40% by weight PAS from example 1, 45% by weight electrolyteand 15% acetylene black was suspended in acetonitrile to form a slurry.The electrolyte was a gel electrolyte made from polyethylene oxide,propylene carbonate, ethylene carbonate, and LiSO₃ CF₃. The slurry wasfinally ground and then cast as a film onto a nickel foil. The entireunit was then dried in a vacuum oven at 40° C.-80° C. for 24 hours.

Preparation of Rechargeable Batteries Example 4

A rechargeable lithium battery of unipolar sandwich design was preparedby sandwiching a polymer electrolyte of about 25 micron thicknessbetween a lithium foil of 125 micron thickness and the composite cathode(example 3) of about 25-75 microns thick. To obtain laboratory prototypecells, the above components were sandwiched between two stainless steelcircular disks having 0.5 cm thickness. A typical material used for theanode was lithium metal. The PAS of the invention prepared in accordancewith the procedure of Examples 1 was used for the cathode. Theelectrolyte employed in preparing the battery of this example was abranched polysiloxane containing grafted ethylene oxide side chains(formula VIII, u=3, v=7, z/w=1, molecular weight of 1000) and a LiSO₃CF₃ salt.

Example 5

Following the general procedure of Example 4, a rechargeablelithium/polymer electrolyte/PAS battery was prepared, using thecomposite cathode of example 2, a lithium foil anode, 9.8 mg of polymergel electrolyte and 2.3 mg of ultrafine graphite powder. The compositeanode contained 7.1 mg of PAS. The polymer gel electrolyte containedpolyacrylonitrile, ethylene carbonate, propylene carbonate and LiCO₄with a conductivity of 3×10⁻³ S/cm at 25° C.

Example 6

Another rechargeable lithium cell was prepared having a compositecathode containing 5.4 mg of polymer gel electrolyte, 12.0 mg of PAS ofExample 1 and 1.9 mg of graphite powder. Assuming a mid cell potentialof 2.5 V, a storage energy of 12.6 mWh was obtained.

Example 7

A rechargeable lithium battery was prepared having a lithium foil of 125micron thickness, a fiber reinforced 1 M LiClO₄ in propylenecarbonate/dimethoxyethane electrolyte and the PAS-based compositecathode of example 2. The cathode contained 50% by weight PAS, 40% byweight PAN, and 10% by weight acetylene black. The battery prepared forthis example exhibited about 500 cycles with a maximum cathode capacityloss of 10% compared to the first cycle. The cells were subjected to atwenty minute quick discharge/charge cycle without any rest period bytrial and error method to choose the appropriate voltage and currentlimits. The average material utilization during the first 200 cycles was72% and about 60% between the 250th and 425th cycle. The cycleefficiency defined as the ratio between charge output (discharge) andcharge input (charge) to thee cell during one complete cycle was closeto unity up to 200 cycles. After about the 475th cycle, when thecapacity of the cell declined by 5%, the battery cycling was disruptedto measure the cell impedance. A low cell impedance was observed whichruled out limitations under cathode/electrolyte interface. The decliningcathode capacity after 500 cycles was attributed to the possibleformation of soft dendrites at the lithium anode-polymer electrolyteinterface; therefore, these cells have been classified as anodeperformance limited battery systems.

Example 8

A rechargeable lithium battery was prepared having a lithium foil anodeof 125 micron thickness, a polyethylene oxide (PEO)/LiSO₃ CF₃ solidelectrolyte along with a siloxane (from Example 4)/LiSO₃ CF₃ liquidelectrolyte, a composite cathode containing 50 wt. % PAS from Example 1along with 30 wt. % conductive carbon and 20 wt. % of the PEO/LiSO₃ CF₃electrolyte, wherein the anode and cathode were separated with Celgard™2500. This 1 cm ×1 cm planar battery exhibited 103 cycles at acharge/discharge current of 0.05 mA/cm² with a capacity of 729 mAhr/gfor the first several cycles, which then decayed to a final capacity of243 mAhr/g at cycle 103.

Example 9

A rechargeable lithium battery was prepared having a lithium foil anodeof 125 micron thickness, a composite cathode containing 50 wt. % PASfrom example 1 along with 30 wt. % conductive carbon and 20 wt. % ofPEO/LiSO₃ CF₃ electrolyte, a solid freestanding film electrolyte ofpolyethylene glycol-bis-(methyl methacrylate)/siloxane/LiSO₃ CF₃ whichwas UV cured (crosslinked), and to the cell was added a small amount ofliquid electrolyte containing siloxane (from Example 4)/LiSO₃ CF₃. This1 cm×1 cm planar battery was charged and discharged at a current densityof 0.05 mA/cm² and exhibited a capacity of 1324 mAhr/g for the firstseveral cycles, which then decayed to a final capacity of 296 mAhr/g atcycle 56.

Example 10

A composite cathode was prepared from a physical mixture of 48 wt. % PASmaterial from example 1, 12 wt. % of polyaniline powder in the form ofVersicon™ manufactured by Allied-Signal, Inc., 20 wt. % acetylene black,and 20 wt. % polymer electrolyte. The polymer electrolyte used to formthe composite cathode consisted of a mixture of poly(ethylene oxide) anda branched polysiloxane with ethylene oxide side chains(polysiloxane-graft-(ethylene oxide)7) and LiClO₄ in the ratio of 24ethylene oxide units per lithium. The polymer electrolytes weredissolved in acetonitrile and added to the mixture of PAS, polyanilineand acetylene black to form a viscous slurry. Composite cathodes ofthickness approximately 100 microns were cast onto Ni foil substratesand the solvent evaporated. Cells were assembled containing compositecathodes, branched polysiloxane electrolytes and lithium foil anodes.The open circuit potentials of the cells were about 3.23 volts.

Preparation of Polyacetylene-co-polysulfur From Acetylene and SulfurExample 11

A solution of Na (2.3 g) in liquid ammonia (200 ml) in the presence ofFeCl₃ was stirred until the blue color disappeared. Afterwards,acetylene was passed through the solution for 2 hours (50-70 ml/min) andthen 9.6 g of sulfur was added portionwise during 1 hour. The mixturewas stirred for 2 hours, poured off from the the unreacted sulfur (1.41g), quenched with NH₄ Cl (5.35 g) and left to staid open to evaporateammonia. The residue was poured with water (200 ml) and the polymer wasfiltered off, washed with water until the negative reaction for Cl ionwas fixed and then washed with acetone and dried to furnish 1.0 g of ablack polymer (S 65.6%). The aqueous filtrate was diluted up to 450 mland boiled with 4.5 g of azobisisobutyronitrile (a radical initiator)for 4 hours. The black carbon-like polymer was filtered off, washed anddried (3.36 g, S 77.9%). The filtrate was acidified with concentratedHCl up to pH ca. 2 and the polymer precipitate was filtered off, washedand dried as above (1.5 g, S 60.1%).

Example 12

To a solution of 24 g Na₂ S×9H₂ O in 50 ml of ethanol/water (1:1 ) wasadded 14.4 g of sulfur. The mixture was stirred at room temperature for1 hour. The solvent was removed under vacuum. The residue was dissolvedin 150 ml of DMF, and to the resulting solution was added 8.61 g ofhexachlorobutadiene. The reaction mixture was stirred for 1 hour, andpoured into 300 ml of water. The precipitated product was filtered,washed with water, acetone, methanol, and dried trader vacuum. Yield17.11 g; mp 90°-96° C.

The performance characteristics of the cells prepared in Examples 6, 7,8, and 9 demonstrate that by using the cathode of the invention a veryhigh cathode utilization is readily achieved resulting in energycapacity storage much higher than those achieved by commerciallyavailable batteries.

What is claimed is:
 1. Art electrochemically activepolyacetylene-co-polysulfur material, which in its oxidized state, is ofthe general formula I ##STR7## wherein x ranges from greater than 1 toabout 100, and n is greater than or equal to 2, and saidpolyacetylene-co-polysulfur material does not contain aliphatic oraromatic moieties.
 2. The material of claim 1 wherein saidpolyacetylene-co-polysulfur electroactive material is of formula I,wherein x is greater than 2 and n is greater than
 5. 3. The material ofclaim 1 wherein said polyacetylene-co-polysulfur electroactive materialis of formula I, wherein x is greater than or equal to about 6 and n isgreater than or equal to about
 10. 4. The polyacetylene-co-polysulfurmaterial of claim 1 obtained from the polymerization of acetylene in thepresence of a metal amide and sulfur.
 5. The,polyacetylene-co-polysulfur material of claim 1 wherein said material ofgeneral formula I is comprised of one or more of the structural units offormulas II-VII, ##STR8## wherein m is the same or different at eachoccurrence and is greater than
 2. 6. The composition of claim 5 whereinm is the same or different at each occurrence and is greater than
 3. 7.The composition of claim 5 wherein m is the same or different at eachoccurrence and is equal to or greater than
 6. 8. The composition ofclaim 1 which upon electrochemical reduction and oxidation does notundergo depolymedzation and repolymerization of the polymer backbone. 9.An electric current producing cell comprising:(a) an anode comprised ofa metal selected from the group consisting of metals belonging to groupIA and group IIA of the Periodic Table of the elements; (b) a cathodematerial comprised of a polyacetylene-co-polysulfur material of thegeneral formula I, ##STR9## wherein values for x can range from greaterthan 1 to about 100, and n is equal to or greater than 2; and (c) anelectrolyte.
 10. The cell of claim 9 wherein said electrolyte providesan operating temperature range for the cell of -40° C. to +120° C. 11.The cell of claim 9 wherein said electrolyte provides an operatingtemperature range for the cell of -20° C. to +100° C.
 12. The cell ofclaim 9 wherein said electrolyte provides an operating temperature rangefor the cell of 0° C. to +100° C.
 13. The cell of claim 9, wherein saidanode material is comprised of one or more materials selected from thegroup of alkali metals, alkaline earth metals, alloys containing alkalimetals, carbons intercalated with alkali metals, and conjugated polymersintercalated with alkali metals.
 14. The cell of claim 9 wherein saidanode material is comprised of one or more materials selected from thegroup consisting of lithium-aluminum alloys, lithium intercalatedcarbons, sodium intercalated carbons, sodium-lead alloys, lithium-leadalloys, lithium-tin alloys, lithium-silicon alloys, lithium-aluminumalloys, lithium doped polyacetylenes, sodium doped polyacetylenes,sodium doped polyphenylenes, and lithium doped polyphenylenes.
 15. Thecell of claim 9 wherein said cathode material is comprised of apolyacetylene-copolysulfur material of general formula I, wherein xranges from about 3 to about 100, and n is greater than
 5. 16. The cellof claim 9 wherein said cathode material is comprised of apolyacetylene-copolysulfur material of general formula I, wherein x isequal to or greater than 6 but less than about 100, and n is greaterthan
 5. 17. The cell of claim 9 wherein said cathode material iscomprised of a polyacetylene-copolysulfur polysulfur obtained from thepolymerization of acetylene in the presence of a metal arnide andsulfur.
 18. The cell of claim 9 wherein said cathode material iscomprised of one or more of the structural moieties of formulas II-VII:##STR10## where, in m is the same or different at each occurrence and isgreater than
 2. 19. The cell of claim 18 wherein m is the same ordifferent at each occurrence and is greater than
 3. 20. The cell ofclaim 18 wherein m is the same or different at each occurrence and isequal to or greater than
 6. 21. The cell of claim 9 wherein said cathodematerial does not undergo polymerization and depolymerization of thepolymer backbone on charging and discharging the cell.
 22. The cell ofclaim 9 wherein said cathode material is a composite cathode comprisedof a polyacetylene-co-polysulfur material of general formula I where xis greater than 1 to about 100, and n is equal to or greater than 2; andone or more of the materials selected from the group consisting ofnon-aqueous electrolytes, conductive fillers, and inert binders.
 23. Thecell of claim 22 wherein said composite cathode comprises a conductivefiller selected from the group consisting of conductive carbons,graphites, conductive acetylene blacks, metal powders, metal flakes,metal fibers, and electrically conductive polymers.
 24. The cell ofclaim 23 wherein said electrically conductive polymer is one or morepolymers selected from the group of polyanilines, polyacetylenes,polypyrroles, polythiophenes, polyphenylenes, polyphenylene-vinylenes,polythienylene-vinylenes; and their derivatives.
 25. The cell of claim23 wherein said composite cathode comprises one or more binders selectedfrom the group consisting of polytetrafluoroethylene, fluorinatedpolymers, EPDM rubber, and SBR rubber.
 26. The cell of claim 9 whereinsaid electrolyte is one or more materials selected from the groupconsisting of solid polymer electrolytes, single-ion-containing polymerelectrolytes, gel polymer electrolytes, and liquid electrolytes.
 27. Thecell of claim 26 wherein said electrolyte is a solid electrolytecomprised of one or more materials selected from the group ofpolysiloxanes, polyphosphazines, polyethylene oxides, polypropyleneoxides, polyacrylonitriles, polyimides, divinyl polyethylene glycols,polyethylene glycol-bis-(methyl acrylates), polyethyleneglycol-bis-(methyl methacrylate); copolymers of the foregoing;derivatives of the foregoing; and crosslinked and networked structuresof the foregoing.
 28. The cell of claim 26 wherein said electrolyte iscomprised of one or more single-ion-conducting polymer electrolytessubstituted with anionic moieties covalently attached to the polymerbackbone.
 29. The cell of claim 26 wherein said gel-polymer electrolyteis comprised of one or more materials selected from the group consistingof polyethylene oxides, polypropylene oxides, polyacrylonitriles,polysiloxanes, polyphosphazines, polyimides, sulfonated polyimides,Nation™ resins, sulfonated polystyrenes, divinyl polyethylene glycols,polyethylene glycol-bis-(methyl acrylates), polyethyleneglycol-bis(methyl methacrylate); blends of the foregoing; derivatives ofthe foregoing; copolymers of the foregoing; and crosslinked and networkstructures of the foregoing; to which has been added one or moregel-forming agents selected from the group of ethylene carbonate,propylene carbonate, acetonitrile, N-methyl acetamide, sulfolane,1,2-dimethoxyethane, polyethylene glycols, 1,3-dioxanes, glymes,siloxanes, polyethylene oxide grafted siloxanes, andmethoxytetrahydrofuran; and which said gel electrolyte further comprisesone or more ionic salts selected from the group consisting of MClO₄,MAsF₆, MSO₃ CF₃, MSO₃ CH₃, MBF₄, MB(Ph)₄, MPF₆, MC(SO₂ CF₃)₃, MN(SO₂CF₃)₂, ##STR11## where M is Li or Na.
 30. The cell of claim 29 whereinsaid gel forming agent is comprised of a material of formula VII,##STR12## wherein u is an integer equal to or greater than 1, v is aninteger equal to or greater than 0 and less than about 30, andthe ratioz/w is equal to or greater than
 0. 31. The cell of claim 26 wherein saidelectrolyte comprises one or more alkali-metal salts selected from thegroup consisting of MClO₄, MAsF₆, MSO₃ CF₃, MSO₃ CH₃, MBF₄, MB(Ph)₄,MPF₆, MC(SO₂ CF₃)₃, MN(SO₂ CF₃)₂, ##STR13## .
 32. Am electric currentproducing cell comprising:(a) an anode comprising one or more materialsselected from the group of alkali metals, alkali metal intercalatedcarbons, alloys containing alkali metals, and alkali metal dopedconjugated polymers; (b) a cathode material comprised of apolyacetylene-co-polysulfur material of general formula I, ##STR14##wherein x is greater than 1 to about 100, n is equal to or greater than2, and said polyacetylene-copolysulfur material is derived from thepolymerization of acetylene in the presence of sulfur; and (c) anelectrolyte comprised of one or more gel-polymer electrolytes selectedfrom the group consisting of polyethylene oxides, polypropylene oxides,polyacrylonitriles, polyimides, sulfonated polyimides, Nafion™ resins,sulfonated polystyrenes, polyethers, divinyl polyethylene glycols,polyethylene glycol-bis-(methyl acrylates), polyethyleneglycol-bis(methyl methacrylate); blends of the foregoing; derivatives ofthe foregoing; copolymers of the foregoing; and crosslinked and networkstructures of the foregoing; to which has been added one or moregel-forming agents selected from the group of ethylene carbonate,propylene carbonate, acetonitrile, N-methyl acetamide, sulfolane,1,2-dimethoxyethane, polyethylene glycols, 1,3-dioxane, glymes,siloxanes, polyethylene oxide grafted siloxanes, and methoxytetrahydrofuran; and which further comprises one or more ionic saltsselected from the group consisting of MClO₄, MAsF₆, MSO₃ CF₃, MSO₃ CH₃,MBF₄, MB(Ph)₄, MPF₆, MC(SO₂ CF₃)₃, MN(SO₂ CF₃)₂, ##STR15## .
 33. Anelectric current producing cell comprising:(a) an anode comprising oneor more metals selected from the group of lithium metal and sodium metal(b) a composite cathode comprised of:(i) a polyacetylene-co-polysulfurmaterial of general formula (C₂ S_(x))_(n), wherein x is greater than 1to about 100 and n is equal to or greater than 2; (ii) an electrolytecomprising an ionic salt selected from the group of Li(SO₃ CF₃), MC(SO₂CF₃)₃, MN(SO₂ CF₃)₂, ##STR16## and a polymer comprising a materialselected from the group of divinyl polyethylene glycols, polyethyleneglycol-bis-(methyl acrylates), and polyethylene glycol-bis(methylmethacrylate) cured by UV, x-ray, gamma ray, electron beam, or otherionizing radiation; polysiloxanes, ethylene oxide grafted siloxanes, andpolyethylene oxide; which optionally further contains a liquid gelationagent; (iii) a conductive filler selected from the group of conductivecarbons, acetylene blacks, and graphite; and (c) an electrolytecomprised of one or more materials selected from the group ofpolysiloxanes, polyphosphazines, polyethers, polyethylene oxides, cureddivinyl polyethylene glycols, cured polyethylene glycol-bis-(methylacrylates), and cured polyethylene glycol bis-(dimethyl acrylates);which electrolyte further comprises a liquid gelation agent and one ormore alkali metal salts selected from the group consisting of MClO₄,MAsF₆, MSO₃ CF₃, MSO₃ CH₃, MBF₄, MB(Ph)₄, MPF₆, MC(SO₂ CF₃)₃, MN(SO₂CF₃)₂, ##STR17## where M is Li or Na.